<ul>
    <li *ngFor="let item of treelists">
      <button md-button (click)="itemClick(item)">{{item.title}}</button>
      <!--调用组件本身并 传值给下级: [treelists]="item.items"-->
      <app-dept-tree-area *ngIf="item._open && item.items && item.items.length" [treelists]="item.items"></app-dept-tree-area>
    </li>
  </ul>